Carpal tunnel syndrome and its relationship to occupation: a meta-analysis

Objective. To examine the association between work place exposure and CTS by meta-analysis, including analyses with respect to exposure to hand force, repetition, vibration and wrist posture. Methods. All relevant peer-reviewed articles published between January 1980 and December 2009 were identified by a systematic search using the MEDLINE, CINAHL and PubMed databases. Papers were critiqued independently by two researchers and the relevant exposure information was extracted. Using the raw data of exposed and unexposed cases, a cumulative effect of specific exposure risks were calculated for hand force, repetition, a combination of force and repetition, vibration and wrist posture using the statistical program, Stata version 11 (StataCorp, College Station, TX, USA). Heterogeneity, meta-regression, publication bias and subgroup sensitivity analyses were performed. Results. Thirty-seven studies from English-language literature met the inclusion criteria. Using National Institute for Occupational Health and Safety criteria for case definition, a significant positive association between CTS and hand force, repetition, use of vibratory tools and wrist posture was observed with approximate doubling of risk for all exposures. Significant heterogeneity among studies was observed for most exposures and metaregression analyses identified CTS case definition, study design, country and risk of bias score to be the significant determinants. When a more conservative definition of CTS was employed to include nerve conduction abnormality with symptoms and/or signs, risk factors significantly associated with an increased risk of CTS among exposed workers were: vibration [odds ratio (OR) 5.40; 95% CI 3.14, 9.31], hand force (OR 4.23; 95% CI 1.53, 11.68) and repetition (OR 2.26; 95% CI 1.73, 2.94). There was a non-significant trend for the association between CTS and combined exposure to both force and repetition (OR 1.85; 95% CI 0.99, 3.45) and wrist posture (OR 4.73; 95% CI 0.42, 53.32). Conclusion. Occupational exposure to excess vibration, increased hand force and repetition increase the risk of developing CTS. Workplace strategies to avoid overexposure to these risk factors should be implemented.